OTTAWA (CP) - Key U.S. security agencies warn that terrorists might exploit pictures of sensitive facilities such as airports that can be routinely viewed by the public through Internet feeds.

A confidential assessment jointly prepared by the FBI and the U.S. Homeland Security Department says online webcams could be a valuable tool for extremists determined to attack critical targets.

The agencies urge government organizations and private-sector partners to ''review the information available on their websites, and balance the public need for information with security concerns.''

The Jan. 10 assessment, obtained by The Canadian Press, was prompted by a recent Internet posting that provided a link to a live webcam at an Alaska airport.

The assessment says the webcam site allowed the viewer to control the camera, providing the ability to zoom in on the airport terminal and cargo areas. Airport authorities disabled the camera after being notified of the posting.

Security officials have focused on bolstering air security since the 9-11 jetliner attacks on New York and Washington.

''The extremist website posting indicates continued terrorist interest in the aviation sector, and suggests that webcams may be a useful planning tool against critical infrastructure targets,'' says the joint assessment.

The Edmonton International Airport took security into account when designing its web camera feature, said Jim Rudolph, a spokesman for the air facility.

Airport cameras offers three views, including two distant shots of runways, but with no ability to zoom in on people or vehicles.

''From a security point of view, we do regard them as being fairly benign,'' said Rudolph.

Webcams have become a widespread and inexpensive means of allowing curious Internet surfers to view real-time feeds of everything from baby eagles to the traffic at busy intersections.

The assessment notes many cameras run by individuals, businesses and government agencies transmit images of weather conditions, famous city squares or geographic highlights, and have little or no surveillance value.

''Webcams at U.S. critical infrastructure locations, however, may allow the open observation of security measures, guard shift changes, and pedestrian and vehicular traffic patterns.''

FBI Special Agent Richard Kolko said that given the countless cameras now on the Internet, there's a need to educate law-enforcement officers as to how they might be misused.

''Sometimes something that's sitting in front of you that's obvious might not be recognizable as something you need to be more alert to,'' he said Thursday from Washington. ''This bulletin helps provide that educational service to them.''

Former CSIS officer David Harris said webcam feeds raise the possibility that facilities are unwittingly equipping their adversaries with tactical information.

He suggested Internet cameras are now luxuries, meaning an end to the virtual eyes trained on airports and other public installations.

''That kind of openness was fun while it lasted, but I'm wondering how workable it is today - whether the convenience, or the aesthetic enjoyment, of having these webcam pictures really is justifiable in light of the threats we face,'' said Harris, a security consultant with Insignis Strategic Research.

''I find myself more and more amazed at how relaxed as a society we can be in North America.''

Harris also wonders whether there is adequate scrutiny of the personnel who operate such devices.

''What kind of screening and clearing arrangements are there for those people who are monitoring these systems, installing them and otherwise responsible for them?'' he said.